A low noise amplifier is an electronic amplifier used to amplify possibly weak signals, for example, captured by using an antenna. The low noise amplifier is placed at the front-end of a radio receiver circuit in some applications. Noise figure and gain are among performance factors to consider for the low noise amplifier. The overall noise figure (NF) of the receiver's front-end is dominated by the first few stages.
The effect of noise from subsequent stages of the receiver chain is reduced by the gain of the low noise amplifier, while the noise of the low noise amplifier itself is injected directly into the received signal. Thus, it is necessary for the low noise amplifier to boost the desired signal power while adding as little noise and distortion as possible, so that the retrieval of the signal is possible in the later stages in the system.